Exploring the Potential of Fulvalene Dimetals as Platforms for Molecular Solar Thermal Energy Storage: Computations, Syntheses, Structures, Kinetics, and Catalysis

Börjesson, Karl; Ćoso, Dušan; Gray, Victor; Grossman, Jeffrey C.; Guan, Jingqi; Harris, Charles B.; Hertkorn, Norbert; Hou, Zhengmeng; Kanai, Yosuke; Lee, Donghwa; Lomont, Justin P.; Majumdar, Arun; Meier, Steven K.; Moth‐Poulsen, Kasper; Myrabo, Randy L.; Nguyen, Son C.; Segalman, Rachel A.; Srinivasan, Varadharajan; Tolman, Willam B.; Vinokurov, N. A.; Vollhardt, K. Peter C.; Weidman, Timothy W.

doi:10.1002/chem.201404170

Cited by 38 publications

(16 citation statements)

References 125 publications

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“…However, these materials were soon abandoned due to low cyclability, limiting long‐term use. In other approaches, new materials with modest energy storage (56 Wh kg −1 ) employing ruthenium with higher cyclability have been developed, but remain prohibitively expensive for wide adoption. With the availability of accurate computational tools, new approaches have leveraged carbon nanostructures and insights into the steric interaction of STFs to increase energy density employing highly cyclable and modest energy density (60–70 Wh kg −1 ) azobenzene derivatives .…”

Section: Introductionmentioning

confidence: 99%

Solid‐State Solar Thermal Fuels for Heat Release Applications

Zhitomirsky

Cho

Grossman

2015

Advanced Energy Materials

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100

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56 Wh kg −1 ) employing ruthenium with higher cyclability have been developed, [5][6][7] but remain prohibitively expensive for wide adoption. With the availability of accurate computational tools, new approaches have leveraged carbon nanostructures and insights into the steric interaction of STFs to increase energy density employing highly cyclable and modest energy density (60-70 Wh kg −1 ) azobenzene derivatives. [ 8,9 ] While demonstrating a per-molecule increase in energy density via templating, [ 10 ] these approaches require complex multistep reactions, have low yields, and the resulting material has low solubility in most organic solvents (<1 g L −1 ). More recently, it was possible to develop liquid azobenzene fuels at room temperature by attaching bulky ligands to the molecule, [ 11 ] and with several computational works detailing the possibility of increasing its energy density through functionalization of the benzene rings, [ 12 ] this platform holds much promise for future STF developments. With such rapid progress in STF materials, it is perhaps surprising that the solid-state platform and related applications have remained largely unexplored, with only recent studies on semi-solid photoliquefi able ionic crystals reaching energy densities of 35 Wh kg −1 . [ 13 ] Transitioning fully to the solid-state offers the possibility of integrating STF materials into a multitude of existing solid-state devices such as coatings for deicing, or novel applications such as solar blankets and other consumer oriented heating equipment.We took the view that if properly engineered on the molecular level, STF materials could be controllably tailored within the solid-state, and that until now, there has not been an efficient method to accomplish this. For one, the most recent STF reports have relied on carbon scaffolds [ 10,14 ] that simultaneously increase synthesis complexity, cannot be deposited into uniform fi lms, contribute to the optical density without resulting in photocharging, and introduce uncontrollable morphological effects that may limit charging and reversible switching in the solid-state. [ 15 ] Similarly, single-molecule thin fi lms do not make homogenous layers, can often result in crystallization, and melt at low temperatures (≈70 °C for azobenzene) thus limiting their utility in the solid-state. Fortunately, a wealth of literature exists on azobenzene-based materials in solid-state applications for microswitches, microactuators, and sensors. [16][17][18][19][20][21] We postulated that the ideal material class to form solid-state STF coatings would need to (1) form smooth fi lms with controllable thickness, (2) be resilient at high temperatures, (3) preserve the heat release properties of Closed cycle systems offer an opportunity for solar energy harvesting and storage all within the same material. Photon energy is stored within the chemical conformations of molecules and is retrieved by a triggered release in the form of heat. Until now, such solar thermal fuels (STFs) have been largely unavailable...

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Section: Introductionmentioning

confidence: 99%

Solid‐State Solar Thermal Fuels for Heat Release Applications

Zhitomirsky

Cho

Grossman

2015

Advanced Energy Materials

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100

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“…The stored energy can be released on demand by applying heat or by using a catalyst to trigger the thermal back isomerization ( Scheme 1 ). Various molecular designs have been explored in this context, including ruthenium compounds, azobenzene derivatives, norbornadiene (NBD) derivatives, dihydroazulenes, and others . The requirements for an efficient MOST system can be summarized as: (i) good spectral overlap of parent molecule absorptions with the solar spectrum, (ii) minimal absorption of the high energy isomer in the solar spectrum, (iii) high quantum yield for the photoisomerization, (iv) high energy storage density, (v) high kinetic stability of the metastable photoisomer, and (vi) high cyclability.…”

Section: Introductionmentioning

confidence: 99%

Liquid Norbornadiene Photoswitches for Solar Energy Storage

Dreos

Wang

Udmark

et al. 2018

Advanced Energy Materials

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been widely implemented [1] but longterm storage of the heat at higher temperatures remains a challenge, limiting broader applications of solar heating. [2,3] Solar thermal energy can be stored for example as thermal energy in rocks or hot water, in phase change materials, [4,5] or in thermochemical energy storage materials. [6] A particular challenge is to identify compact thermal storage solutions capable of operating in the medium temperature range (100-180 °C). [2] In this context, one possible solution is to use molecular photoswitches where the solar energy is stored in high energy photoisomers. [7] This way of storing solar energy has been referred to as molecular solar thermal (MOST) [8] energy storage or solar thermal fuels. [9] MOST systems are based on a parent molecule, which upon irradiation photoisomerizes to a highenergy isomer. The stored energy can be released on demand by applying heat or by using a catalyst to trigger the thermal back isomerization (Scheme 1). [7,10,11] Various molecular designs have been explored in this context, including ruthenium compounds, [8,12] azobenzene derivatives, [13][14][15][16][17][18] norbornadiene (NBD) derivatives, [10,11,19] dihydroazulenes, [20] and others. [21] The requirements for an efficient MOST system [7,10,22] can be summarized as: (i) good spectral overlap of parent molecule absorptions with the solar spectrum, (ii) minimal absorption of the high energy isomer in the solar spectrum, (iii) high quantum yield for the photoisomerization, (iv) high energy storage density, (v) high kinetic stability of the metastable photoisomer, and (vi) high cyclability. It is also fundamental to obtain neat liquid or solid functional MOST materials (depending on the desired applications), since dilution in solvents or solid matrix lowers the energy storage density. A closed MOST system has been previously described, [23] which involves cycles of an MOST fluid in a solar collector for the photoconversion, a storage tank, and a heat extractor part (see Scheme 1).NBD (1 in Scheme 1) and its derivatives undergo photoisomerization to the highly strained quadricyclane (QC, 2 in Scheme 1) upon irradiation with UV or visible light. [24] By molecular design, the system has been optimized toward MOST applications, and the best NBD derivatives fulfil several of the requirements for a functional system, such as high photoisomerization quantum yield, redshifted absorption, high energy storage densities, and very long half-life of the Due to high global energy demands, there is a great need for development of technologies for exploiting and storing solar energy. Closed cycle systems for storage of solar energy have been suggested, based on absorption of photons in photoresponsive molecules, followed by on-demand release of thermal energy. These materials are called solar thermal fuels (STFs) or molecular solar thermal (MOST) energy storage systems. To achieve high energy densities, ideal MOST systems are required either in solid or liquid forms. In the case of the latter, neat high ...

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“…The stored energy is then released in form of heat when the metastable isomers are reverted to the thermodynamically stable ones upon appropriate stimuli. Various photoswitches, including azobenzenes, [6] norbornadienes, [7] dihydroazulenes, [8] and fulvalene dirutheniums, [9] are currently investigated for their potential as the energy storage materials, and approaches such as molecular engineering [10] and templated assembly [11] have been reported to improve the energy storage performance. However, the development of solar thermal battery is still severely limited by (i) the low energy density that can be afforded by the photoisomerization reactions and (ii) the fast self-discharging effect resulting from the instability of the metastable isomers.…”

Section: Introductionmentioning

confidence: 99%

Efficient Co-Harvesting of Solar Energy and Low-Grade Heat by Molecular Photoswitches for High Energy Density, Long-Term Stable Solar Thermal Battery

Zhang¹,

2019

Preprint

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Solar energy and ambient heat are two inexhaustible energy sources for addressing the global challenge of energy and sustainability. Solar thermal battery based on molecular switches that can store solar energy and release it as heat has recently attracted great interest, but its development is severely limited by both low energy density and short storage stability. On the other hand, the efficient recovery and upgrading of low-grade heat, especially that of the ambient heat, has been a great challenge. Here we report that solar energy and ambient heat can be simultaneously harvested and stored, which is enabled by room-temperature photochemical crystal-to-liquid transitions of small-molecule photoswitches. The two forms of energy are released together to produce high-temperature heat during the reverse photochemical phase change. This strategy, combined with molecular design, provides high energy density of 320-370 J/g and long-term storage stability (half-life of about 3 months). On this basis, we fabricate high-performance, flexible film devices of solar thermal battery, which can be readily recharged at room temperature with good cycling ability, show fast rate of heat release, and produce high-temperature heat that is >20<sup> o</sup>C higher than the ambient temperature. Our work opens up a new avenue to harvest ambient heat, and demonstrate a feasible strategy to develop high-performance solar thermal battery.

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Exploring the Potential of Fulvalene Dimetals as Platforms for Molecular Solar Thermal Energy Storage: Computations, Syntheses, Structures, Kinetics, and Catalysis

Cited by 38 publications

References 125 publications

Solid‐State Solar Thermal Fuels for Heat Release Applications

Solid‐State Solar Thermal Fuels for Heat Release Applications

Liquid Norbornadiene Photoswitches for Solar Energy Storage

Efficient Co-Harvesting of Solar Energy and Low-Grade Heat by Molecular Photoswitches for High Energy Density, Long-Term Stable Solar Thermal Battery

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